94 Q45 starting system problem

[94 Q45]

Hi, I tried to start the car at night today and I would not start, it just crank. I checked the battery connection and battery charge condition and it was good. I have this problem since I got the car, sometimes someday it starts fine but sometimes it just would not start, it just crank. Has anyone experienced this before and what do you think the problem would be? Thank you.

[Q45denver]

How many miles since you last replaced the fuel pump?

[maxnix]

And fuel filter? ISO-HEET? BG44K?

[94 Q45]

Hi, I just bought this car with 150K mile on it and I have no idea if the fuel pump is previouly replaced by anybody, it looks like it has not been properly maintain by the previous owner, so I think fuel pump and filter has not been change for a very long time. After reading the fuel pump problem post I think the problem is on the fuel pump becaue I now noticed when I turn the key to the ON position from the OFF position, the fuel pump doe not make any audible "buzz" noise that would indicate the pump is activating as I noticed this sound in my other car from the truck area. I also noticed a sound from the trunk area when I step on the gas pedal with the key on ON position. I wonder if the fuel pump is bad and is there any way to check it? I have not checked the condition of the spak plug yet, maybe it is the spark plug because I read in a 1996 TSB describing the same sympton that is occuring to the Q45 and it said the cause is the dirty spark plug or a problem in ignition timing or idle. Thank you for the quick response and help.

[maxnix]

Owner can obtain the Infiniti dealer performed service history by submitting the VIN to your friendly service writer, or orally by registering your with Infiniti Customer Service as the new owner.

It might well be your FPCU is fried by a failed fuel pump. I would leave the spark plug question alone for now, unless the haven't been changed for >50K miles. Then just change them. Not sure which TSB you are referencing.

You can always measure your fuel pressure. Get a FSM and all the TSB from http://www.nissan-techinfo.com/infiniti/ for a one day subscription. Other wise you are just urinating upwind.

[96Qowner]

It might well be your FPCU is fried by a failed fuel pump.

And it's relatively easy to check. The Fuel Pump Controller (FPCU) is located in the trunk bolted to the underside of the rear deck - easy to pull out and check for burn spots. Pictures here:

zerothread?id=34503

If your FPCU is fried, it's because your failing fuel pump pulled too much current through it, so you'll have to replace the fuel pump, too, or it'll just fry the new FPCU. The fuel pump replacement needs to be new, and it's spendy. The FPCU can be a used one, relatively cheap at $50 or less.

You can also bypass the fault and jump the FPCU to ground. This will provide current to the pump to get the car running. The pump will be in high speed mode though (3-speed pump), so it's only a temporary fix, or for troubleshooting:

zerothread?id=18148

[Q45tech]

The FPCU can be a used one, relatively cheap at $50 or less.

Of course many may have been stressed by previous bad fuel pumps.

Standard dealer practice is to change both components to avoid a comeback, unfortunately the changed out FPCU and those from junk yards find their way to ebay, etc.

You may be lucky or not in used purchases.

Many interior failures may not be visible via a discolored [brown] spot on the white socket.

No starts, hiccups, laggy acceleration, or sudden dying are alln some of symptoms.

Always do a measured driving fuel pressure test duplicating ALL the posssible conditions especially WOT extended acceleration to shifts [6000+ rpm].

[94 Q45]

Hi, Thank you for the information. today I just pulled out the inlet hose from the fuel filter and then start cranking the car, I noticed there is no fuel coming out of the fuel filter, does this explain that the fuel pump is bad and does not pump any fuel to start the car. If it is, I will have to buy a fuel pump and maybe the FPCU also. Dos anybody have any idea on where to get a good deal on a decent fuel pump and FPCU or does anybody have fuel pump or FPCU for sale? Thanks in advance.

[maxnix]

Nix on used FP, and used FPCU is a crapshoot, per Q45tech's post above.

http://www.infinitipartsusa.com

Be sure to get the O ring and a fuel filter.

[94 Q45]

Hi, I want to know where is the exact location of the FPCU, I know it is in the rear truck are under the "sundeck", but where is the "sundeck" and can it be reach from the truck area? Also, I have a question on how to check the fuel pump relay, the procedure said to check for continuity with 12 volt DC applied, how do I applied 12 volt DC to the green relay becaue it is connected to a white connector. Thank you for the information.

[elwesso]

if you ground the white wire on the FPCU harness connector and turn the key on, the pump should start up..... It should at least do something, im not sure if ive heard of pumps going so bad they dont even do anything... Its possible its bad enough not to create enough fuel pressure, but it should at least make noise.

if you get a FPCU from a member on NICO it definitely has a better chance of being good than if you got one off ebay... Even older ones seem to be fine as long as they havent had a bad pump on them for any length of time....

The FPCU is easy to identify once you get the gray trunk divider out. Its the harness that goes from the fuel pump to the FPCU.

[maxnix]

Even older ones seem to be fine as long as they havent had a bad pump on them for any length of time.....

Then there was the one that had an intermittant fault on Q45tech's car that took him over a year to diagnose. No abused pumps involved, either.
Modified by maxnix at 12:18 PM 9/12/2006

[elwesso]

thing is though, you could buy 3 used ones and still be well under what a brand new one costs....

For me, its worth it.

[Q45tech]

Agreed the probabilities are in favor that 1 out 4 used [ebay] might act nearly like new for awhile.

As long a you install and load test each one for proper operation [make sure they switch among the 3 speeds] ......................easy measure current thru the fuel pump fuse..............3 rising steps of current from warm idle, high cruise, and WOT high rpm [above 5,000].

I'm lucky in that we have some records on many wrecked/blown Q we buy for parts and can see some of what has been changed.

[maxnix]

Yeah, off eBay, one could get a string of bad ones from unscrupulous seller's.

Measurement and testing is the only way, if not buying new.

[94 Q45]

Hi, Thank you all people for the reply, it helps me a lot. Does anybody know if a 90 or 92 Q45 FPCU would fit in the 94 Q45? Are they the same? I am just doing a replacement of the old bad FPCU and fuel pump. Thank you.

[Q45tech]

The 90-96 FPCU are pretty much identical.............obviously the newer the better, balanced against mileage and where the car was used.

Electronics fail faster in hot climates [Arizona/Kuwait/Kalahari] luckily the trunk is cooler than engine compartment.....................the capacitors have a life vs temperature curve [just like the Bose Amps].

Since I have been driving for 45+ years, I remember fondly that the old mechanical fuel pumps got changed every 2-3 years and many 70-80's cars failed every year when electric first came out.

I think 7 years is great phenominal life! Considering the pump runs continuously without any maintenance. Few use BG44k to clean corrosion quarterly.